SCBA (self contained breathing apparatus) is worn by hazardous environment workers such as firemen and industrial safety personal when entering an area that may contain poisonous gas, smoke or other environment which requires the use of a SCBA. Such equipment usually includes a PASS (personal alert safety system, with requirements defined by National Fire Protection Association NFPA 1982 with revisions in 1988 and 1994). The PASS activates an alarm if the worker stops moving for a predetermined period of time. The alarm is a noise generator on the PASS and/or a device that transmits radio waves to a nearby receiver, to alert others that the worker may be in trouble. It is common for a PASS to generate a moderately loud chirping sound after a specified time, that is usually twenty seconds plus five or minus three seconds, if the worker does not move, and to generate the full alarm after thirty seconds plus or minus five seconds if the worker still has not moved.
Previous PASS circuits had manual switches to turn them on and off, or set and reset, and the worker was supposed to turn on the PASS whenever he put on the equipment. However, many workers did not operate the on switch. One reason is that some workers forgot to operate the switch when they first put on the equipment, and some workers thought they would operate the switch when they put on their face mask just before entering the hazardous environment, but forgot to do so. A low cost system which automatically turned on or set the PASS whenever a worker wore the equipment, would increase safety for hazardous environment workers.